DCMTK

How to reproduce:

• Run a storescp configured to convert VR=UN encoded attributes to real VR.
• Send a Implicit VR Little Endian encoded image that contains a VR=UN sequence of a known attribute.
• The storescp will fail to receive the image with error messages indicating that it encountered an unknown VR.
• Interestingly dcmconv doesn't display the same issue

Patch to enable recover-VR for storescp:

--- a/dcmnet/apps/storescp.cc
+++ b/dcmnet/apps/storescp.cc
@@ -342,7 +342,10 @@ int main(int argc, char *argv[])
     cmd.addSubGroup("data set trailing padding (not with --write-dataset or --bit-preserving):");
       cmd.addOption("--padding-off",            "-p",      "no padding (default)");
       cmd.addOption("--padding-create",         "+p",   2, "[f]ile-pad [i]tem-pad: integer",
-                                                           "align file on multiple of f bytes and items\non multiple of i bytes");
+                                                 "align file on multiple of f bytes and items\non multiple of i bytes");
+    cmd.addSubGroup("handling of defined length UN elements:");
+      cmd.addOption("--retain-un",           "-uc",    "retain elements as UN (default)");
+      cmd.addOption("--convert-un",          "+uc",    "convert to real VR if known");
 #ifdef WITH_ZLIB
     cmd.addSubGroup("deflate compression level (only with --write-xfer-deflated/same):");
       cmd.addOption("--compression-level",      "+cl",  1, "[l]evel: integer (default: 6)",
@@ -789,6 +792,17 @@ int main(int argc, char *argv[])
     }
     cmd.endOptionBlock();

+    cmd.beginOptionBlock();
+    if (cmd.findOption("--retain-un"))
+    {
+      dcmEnableUnknownVRConversion.set(OFFalse);
+    }
+    if (cmd.findOption("--convert-un"))
+    {
+      dcmEnableUnknownVRConversion.set(OFTrue);
+    }
+    cmd.endOptionBlock();
+
 #ifdef WITH_ZLIB
     if (cmd.findOption("--compression-level"))
     {

A patch that seems to fix the bug:

--- a/dcmdata/libsrc/dcitem.cc
+++ b/dcmdata/libsrc/dcitem.cc
@@ -4306,7 +4306,7 @@ OFCondition DcmItem::newDicomElement(DcmElement *&newElement,

         // sequences and items:
         case EVR_SQ :
-            newElement = new DcmSequenceOfItems(tag, length);
+         newElement = new DcmSequenceOfItems(tag, length, readAsUN);
             break;
         case EVR_na :
             if (tag.getXTag() == DCM_Item)

Reported 2019-06-21 by Jesper Bojesen <jbojesen@vitalimages.com>